Make nesting/running states a RunLoop rather than a MessageLoop concept.

chrome/browser/ui/views/simple_message_box_views.cc

Index: chrome/browser/ui/views/simple_message_box_views.cc
diff --git a/chrome/browser/ui/views/simple_message_box_views.cc b/chrome/browser/ui/views/simple_message_box_views.cc
index 91c219394eff2a5b098cd8d88d6deecae3c9b67b..a7f703744ee77f0e03ac2618ed09ac284e514ba9 100644
--- a/chrome/browser/ui/views/simple_message_box_views.cc
+++ b/chrome/browser/ui/views/simple_message_box_views.cc
@@ -222,8 +222,7 @@ MessageBoxResult ShowMessageBoxImpl(gfx::NativeWindow parent,
   // ResourceBundle is not initialized yet.
   // Fallback to logging with a default response or a Windows MessageBox.
 #if defined(OS_WIN)
-  if (!base::MessageLoopForUI::IsCurrent() ||
-      !base::MessageLoopForUI::current()->is_running() ||
+  if (!base::RunLoop::IsRunningOnCurrentThread() ||
       !ResourceBundle::HasSharedInstance()) {
     LOG_IF(ERROR, !checkbox_text.empty()) << "Dialog checkbox won't be shown";
     int result = ui::MessageBox(views::HWNDForNativeWindow(parent), message,